Such a watch is disclosed, for example, in FR patent 1557197. The attachment of the watch case to the strap or bracelet is achieved using a ring whose inner surface is adjusted to the diameter of the cylindrical side surface of a back-calotte forming the main element of the case. The ring is driven into the back-calotte. The drawback of driving in the ring is that it makes it difficult for the user to remove the ring to separate the strap or bracelet from the watch case, in particular for a user who is not strong. It is therefore difficult to change the strap. Further, if the ring is not properly adjusted, there is a risk that it will not remain fixed to the case and retain the strap. The assembly is then likely to come apart easily.
U.S. Pat. No. 4,742,503 and EP Patent 0379540 disclose devices for the removable assembly of a strap to a watch case by means of a bezel or a ring allowing the strap to be changed easily. However, in these devices, the bezel or ring appears visibly around the watch case, which impairs the aesthetic appearance of the watch.
EP Patent 0758767 discloses a device for the removable assembly of a strap to a watch case by means of a ring integral with the strap. Each of the bracelets owned by the user to change the appearance of his watch must therefore be fitted with a mounting ring, which increases the cost of the assembly. Further, the ring is mounted around the case on the dial side, so that it appears visibly around the watch dial, which impairs the aesthetic appearance of the watch.